The invention relates to a method and a system for adjusting a lambda value of the air/fuel mixture supplied to an internal combustion engine during the transition from a lower load range to a upper load range.
Such a method and such an adjusting system are known from DE-C2-33 41 720. The system includes an adjusting means which outputs, in dependence on a respective value of a accelerator pedal position signal supplied to it, an adjusting signal to a throttle flap actuator for adjusting the air volume supplied to the internal combustion engine in such a manner that a lean air/fuel mixture is obtained below a position threshold value of the accelerator pedal position signal which marks the boundary between the lower and upper load range. The system operates in such a manner that shortly before the threshold value is reached, the throttle flap is completely open. If, finally, correspondence between the threshold value and the value of the accelerator pedal position signal is achieved, the throttle flap is reset by a predetermined value which can depend on the rotational speed and the accelerator pedal position. The resetting occurs to such an extent that a rich mixture is obtained in the upper load range, even if the throttle flap is again opened further with further increase in the value of the accelerator pedal position signal past the position threshold value.
Operating at a lambda value of less than 1 in the upper load range results in an increased pollutant emission.